Find index of last occurrence of a substring in a string

Question

I want to find the position (or index) of the last occurrence of a certain substring in given input string str.

For example, suppose the input string is

Answer 1

If you don't wanna use rfind then this will do the trick/

def find_last(s, t):
    last_pos = -1
    while True:
        pos = s.find(t, last_pos + 1)
        if pos == -1:
            return last_pos
        else:
            last_pos = pos